const fs=require('fs');
var data ='这是我要写入的内容！\n';

var wrs=fs.createWriteStream('data.txt',{flags:'a+'});

wrs.write(data);
wrs.end();
wrs.on('finish',function(){
    console.log('写入完成！');
});

wrs.on('error',function(err){
    console.log(err);
});